Between 1939 and 1945 at least 1.5 million Polish citizens were transported to the Reich for labor, most of them against their will. Many were teenaged boys and girls. Although Germany also used forced laborers from western Europe, Poles, along with other eastern Europeans viewed as inferior, were subject to especially harsh discriminatory measures. They were forced to wear identifying purple P's sewn to their clothing, subjected to a curfew, and banned from public transportation. While the actual treatment accorded factory workers or farm hands often varied depending on the individual employer, Polish laborers as a rule were compelled to work longer hours for lower wages than western Europeans, and in many cities they lived in segregated barracks behind barbed wire. Social relations with Germans outside work were forbidden, and sexual relations with them were considered "racial defilement" punishable by death. During the war hundreds of Polish men were executed for their relations with German women.

Poles were prisoners in nearly every camp in the extensive camp system in German-occupied Poland and the Reich. A major camp complex at Stutthof, east of Danzig, existed from September 2, 1939, to war's end, and an estimated 20,000 Poles died there as a result of executions, hard labor, and harsh conditions. Auschwitz (Oswiecim) became the main concentration camp for Poles after the arrival there on June 14, 1940, of 728 men transported from an overcrowded prison at Tarnow. By March 1941, 10,900 prisoners were registered at the camp, most of them Poles. In September 1941, 200 ill prisoners, most of them Poles, along with 650 Soviet prisoners of war, were killed in the first gassing experiments at Auschwitz. Beginning in 1942, Auschwitz's prisoner population became much more diverse, as Jews and other "enemies of the state" from all over German-occupied Europe were deported to the camp.

The Polish scholar Franciszek Piper, the chief historian of Auschwitz, estimates that 140,000 to 150,000 Poles were brought to that camp between 1940 and 1945, and that 70,000 to 75,000 died there as victims of executions, of cruel medical experiments, and of starvation and disease. Some 100,000 Poles were deported to Majdanek, and tens of thousands of them died there. An estimated 20,000 Poles died at Sachsenhausen, 20,000 at Gross-Rosen, 30,000 at Mauthausen, 17,000 at Neuengamme, 10,000 at Dachau, and 17,000 at Ravensbrueck. In addition, victims in the tens of thousands were executed or died in the thousands of other camps—including special children's camps such as Lodz and its subcamp, Dzierzazn—and in prisons and other places of detention within and outside Poland.